1. Field of the Invention
The present invention relates to an image forming apparatus such as an electrophotographic copying apparatus and, more particularly, to exposing means for exposing a photosensitive body.
2. Related Background Art
Conventionally, in an apparatus of the above sort, as disclosed in Japanese Laid-Open Patent Application Nos. 48-71240 and 57-201267, light rays generated by a single light source are split into two light components by a reflecting plate. One component is radiated onto the surface of a photosensitive body as preexposure light (exposure light for erasing the residual charge on the entire surface of the photosensitive body before the photosensitive body is charged), and the other as blank exposure light (exposure light for erasing only the residual charge except that on an image region after the photosensitive body is charged).
In Japanese Laid-Open Patent Application No. 48-71240, only unnecessary image regions at the leading and the trailing ends of an image formed on the surface of a photosensitive body are erased by blank exposure light and a shutter is provided for selectively shielding the blank exposure light. In Japanese Laid-Open Patent Application No. 57-201267, a shutter having the above function is divided into a plurality of portions in the axial direction of a photosensitive body, and each divided portion of the shutter can selectively shield exposure light. Therefore, images that are enlarged or reduced at various magnifications can be processed.
The apparatus disclosed in Japanese Laid-Open Patent Application No. 48-71240, however, cannot process enlarged or reduced images because the apparatus has only the function of erasing unnecessary image regions at the leading and the trailing ends of an image. In addition, in order for the apparatus disclosed in Japanese Laid-Open Patent Application No. 57-201267 to meet various magnifications, it is necessary to arrange shutters in a number corresponding to the number of magnifications, resulting in a complicated and bulky apparatus.